Probe cleaning sheet and cleaning method

ABSTRACT

A probe cleaning sheet is provided, which can be used not only at a room temperature and high temperature but also in a low temperature environment with sufficient cushioning property and which can softly and efficiently clean a probe tip end. Specifically, the cleaning sheet has a layered structure including an elastic layer below a polishing layer, for removing, by contact with the polishing layer, foreign matter adhered on a tip end of a probe for semiconductor inspection, and the elastic layer is a polytetrafluoro-ethylene porous body layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe cleaning sheet for removing foreign matter adhered to a tip end of a probe for inspecting a semiconductor used for testing (inspecting) electrical characteristics of a semiconductor chip. The present invention further relates to a method of cleaning the probe for inspecting a semiconductor using the cleaning sheet in a low temperature environment.

2. Description of the Background Art

In the process of manufacturing semiconductors, defective and non-defective semiconductor chips on which circuit patterns have been formed are sorted using a wafer prober that physically and electrically connects a pad (electrode portion) of a semiconductor chip to a tester. A wafer prober adopting a probe is commonly used. Specifically, as a wafer prober, an apparatus is known in which a probe is brought into contact with a pad of a semiconductor chip (electronic circuit die) such as an IC, LSI or the like formed on the semiconductor wafer, and by an external tester connected to the probe, electrical characteristics are inspected efficiently to identify semiconductor chips that are determined by the tester as defective.

A dominant type wafer prober uses a combination of a probe card or probing card and an IC tester, to inspect electrical characteristics of a semiconductor chip. A probe card plays an important role as it is brought into direct contact with a pad on the semiconductor chip. Typical probe cards with probes include cantilever type and vertical type ones.

In a main structure of a cantilever type probe card, probes are arranged along a horizontal direction, fixed by epoxy resin on a fixing base formed of ceramics referred to as a ring, and the ring is fit in a printed board. Tails of the probes are soldered on a pattern on the printed board, to establish electrical conduction. Tip ends of the probes are bent to be inclined and in contact with the pad. Blade type probe cards, in which probes are soldered onto a metal plate referred to as a blade, are also known as a variation of the cantilever type cards.

In the vertical type probe card, probes are erected vertically. The probe card of this type includes a structure having two substrates between which probes are buckled, a structure in which probes are bent in a prescribed direction, or a structure having a micro-spring. By adopting such structures, significant scratch made by the probe or too much scrubbing of pads can be prevented.

In addition, a probe head type prober has also been known in which each probe is driven independently. The probe head type prober is generally used together with a probe card, and often used partially.

As to the material of probes for inspecting semiconductors for such usage, tungsten is generally used in view of life and cost. Besides, tungsten-rhenium alloy, palladium alloy or beryllium-copper alloy is also used. A probe having the tip end coated or heat-treated to suppress adhesion of foreign matter has been known. Typically, the probe is formed to have a spherical tip end, to enable smooth contact with the pad.

The pad (electrode portion) of a semiconductor chip is formed of aluminum or aluminum-copper alloy. When electrical characteristics of a semiconductor chip are to be inspected using a probe card, a hard probe is brought into press-contact with a pad on the semiconductor chip. Therefore, foreign matter such as aluminum powder scraped off from the pad adheres to the tip end of the probe. Adhesion of foreign matter such as aluminum powder to the tip end of the probe causes conduction failure between the probe and the pad, or degrades electrical contact, hindering accurate measurement of electrical characteristics of the semiconductor chip. Further, adhesion of foreign matter to the tip end of the probe results in fluctuation of contact resistance of the probe.

In order to remove foreign matter such as aluminum powder adhered to the tip end of the probe, probe tip end is cleaned. In a method of cleaning, a ceramic plate having the same shape as the semiconductor wafer is used, and the probe is brought into press-contact with the ceramic plate through the same operation as probing of the semiconductor wafer. By this method, the probe can be cleaned through the same operation as the inspection of electrical characteristics of the semiconductor wafer. In the method using a ceramic plate, however, the tip end of the probe tends to be scraped away, so that life of the probe card, which is expensive, becomes shorter. When the tip end of the probe is scraped away through repetitive cleaning and the tip end that has been spherical come to have a flat shape, it becomes difficult to realize smooth contact between the probe and the pad.

A method of removing foreign matter by piercing the probe tip into a cleaning member such as silicone rubber or urethane rubber has been known. This method, however, has a disadvantage that fragments of the cleaning member as new foreign matter adhere to the tip end of the probe, or the tip end of the probe is damaged at the time of piercing. Further, foreign matter such as aluminum powder accumulates in the cleaning member, and therefore, cleaning performance degrades quickly.

In order to solve the problems described above, a cleaning sheet for cleaning a probe card has been developed and commercially available (manufactured by Nihon Micro Coating Co. Ltd., trade name “MIPOX”), which is structured to have polyurethane base layer having good cushioning property, a polishing layer containing fine abrasive powder on one surface of the base layer and an adhesive layer on the other surface. Because of this adhesive layer, the cleaning sheet can be used adhered on a substrate such as a silicon wafer. Specifically, when the cleaning sheet is adhered to the substrate and adapted to have the same shape and size as the semiconductor wafer, it becomes possible to bring the probe into press-contact with the surface of the polishing layer of the cleaning sheet to remove foreign matter, through the same operation as probing of the semiconductor wafer.

As the cleaning sheet for removing foreign matter adhered to the tip end of a probe, by way of example, Japanese Utility Model Registration No. 3072423 and Japanese Patent Laying-Open No. 11-238768 disclose a cleaning sheet for cleaning tip end of a probe including a cleaning thin film having fine abrasive powder fixed on a surface, an elastic sheet provided below the cleaning thin film, and a substrate provided below the elastic sheet. These references also disclose a cleaning sheet for cleaning a tip end of a probe having a structure including, in place of a cleaning thin film having fine abrasive powder fixed on a surface, a hard metal thin film for cleaning of which surface is made rough, and silicone rubber and urethane rubber are mentioned as material of the elastic sheet.

When such a cleaning sheet having the layered structure in which an elastic layer is arranged below the polishing layer is used and the tip end of the prove is pressed onto the polishing layer, the tip end of the probe softly contacts the polishing layer as there is the elastic layer. Further, even when the prove tip end is brought into press-contact with the polishing layer, the polishing layer is not readily be torn. Therefore, by the cleaning sheet described above, foreign matter can efficiently be removed while wear and damage of the probe tip ends can be suppressed.

The known cleaning sheet, however, employs silicone rubber or urethane rubber (polyurethane) as the elastic layer, and therefore, elasticity (cushioning property) of the elastic layer significantly degrades in a low temperature environment. Particularly, in a low temperature environment of about −30° C., the elastic layer of silicone rubber or polyurethane loses its cushioning property. As a result, amount of wear of the probe tip end increases when cleaned in the low temperature environment, and the life of probe card becomes shorter.

Recently, for semiconductor devices mounted on a car and the like, electrical characteristics of the semiconductor chip formed on a semiconductor wafer are inspected in a low temperature environment of about −30° C. to verify the operation of the semiconductor device in the low temperature environment. When inspection is done in such a low temperature environment, the semiconductor wafer to be inspected and the surroundings are cooled as a whole, and therefore, the probe of the probe card is also cooled and used for inspection.

A plurality of semiconductor wafers are contained in one cassette and set in a wafer prober, and the wafers are taken out one by one from the cassette and placed on a chuck top (base). The probe of the probe card is brought into press-contact with the pad of the semiconductor chip formed on the semiconductor wafer, and electrical characteristics are measured. At this time, when a cleaning sheet having the same shape and size as the semiconductor wafer is mixed among the plurality of semiconductor wafers put in the cassette, the probe can be cleaned automatically. For manual operation also, the cleaning sheet is placed on the chuck top, and the probe is cleaned.

Therefore, when the electrical characteristics of the semiconductor wafer are inspected at a low temperature using the probe for semiconductor inspection, generally, the cleaning sheet for removing foreign matter adhered to the probe tip ends is also used kept at the low atmospheric temperature. If the atmospheric temperature were to be increased to the room temperature only for the cleaning of probes, throughput would be significantly decreased, as it takes long to elevate the temperature.

Some types of wafer probers developed recently allow measurement at a high temperature of up to 150° C., and some types allow measurement both in the high temperature range and in a low temperature range of down to −55° C. Therefore, the cleaning sheet used for cleaning probes for semiconductor inspection should desirably have cushioning property allowing use in a low temperature environment of, for example, −30° C., and have satisfactory performance of efficient cleaning.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a probe cleaning sheet having a layered structure including a polishing layer and an elastic layer arranged therebelow, for removing, by a contact with the polishing layer, foreign matter adhered to a tip end of a probe for semiconductor inspection exhibiting sufficient cushioning property for use not only in room and high temperature environments but also in low temperature environment, and capable of softly and efficiently cleaning the tip end of the probe. Another object is to provide a method of cleaning for removing foreign matter adhered to a tip end of a probe for semiconductor inspection in such a low temperature environment.

By close study, the inventor have found that when a layer of polytetrafluoro-ethylene porous body is arranged as the elastic layer in the probe cleaning sheet having a layered structure including a polishing layer and an elastic layer arranged therebelow, a cleaning sheet of which cushioning property is maintained even in the low temperature environment of 0° C. or lower, even down to about −30° C. can be obtained.

The polytetrafluoro-ethylene porous body (hereinafter referred to as “PTFE porous body”) has high resin strength, and therefore, even if a tip end of a probe pierces through the polishing layer at the time of cleaning, the PTFE porous body would not be torn, and hence there is no possibility of its fragments scattered as foreign matter. By selecting porosity and average pore diameter of the PTFE porous body, sufficient cushioning property can be provided and, in addition, entrance of prove tip end to the pore of PTFE porous body can be prevented even when the tip end of the probe tears the polishing layer. Thus, damage to the probe tip end can be prevented. The present invention is based on these findings.

Thus, the present invention provides a probe cleaning sheet having a layered structure including a polishing layer and an elastic layer arranged therebelow, for removing, by a contact with the polishing layer, foreign matter adhered to a tip end of a probe for semiconductor inspection wherein the elastic layer is a layer of polytetrafluoro-ethylene porous body.

Further, the present invention provides a method of cleaning for removing foreign matter adhered to a tip end of a probe for semiconductor inspection in a low temperature environment of 0° C. or lower, using the probe cleaning sheet.

The probe cleaning sheet of the present invention can be used at a room temperature and high temperature and, in addition, it has sufficient cushioning property in a low temperature environment of about −30° C., so that it can softly and efficiently clean the tip ends of probes. In the probe cleaning sheet of the present invention, the layer of PTFE porous body is not broken by the probe at the time of cleaning, and therefore, new foreign matter does not result. Further, the tip end of the probe is not damaged. The probe cleaning sheet of the present invention can be used for removing foreign matter such as aluminum powder adhered to the tip end of the probe of a wafer prober employing the probe for semiconductor inspection.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross section representing a layer arrangement in accordance with an embodiment of the cleaning sheet of the present invention.

FIG. 2 is a schematic cross section representing a layer arrangement in accordance with another embodiment of the cleaning sheet of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The layer arrangement of the probe cleaning sheet of the present invention (hereinafter simply referred to as a cleaning sheet) will be described with reference to FIGS. 1 and 2. The cleaning sheet of the present invention has a layered structure including a polishing layer and an elastic layer arranged below the polishing layer, and as the elastic layer, a PTFE porous body is arranged. The surface of the polishing layer, which is opposite to the elastic layer, is brought into contact with the tip end of the probe for semiconductor inspection. The cleaning sheet of the present invention may include, as needed, a layer or layers below the elastic layer.

Preferably, the cleaning sheet of the present invention is used adhered to a substrate such as a silicon wafer or a ceramic plate. For this purpose, preferably, an adhesive layer is arranged below the PTFE porous body layer. Preferably, the adhesive layer is arranged below the PTFE porous body layer with a synthetic resin film interposed.

As can be seen from the specific example of layer arrangement shown in FIG. 1, a cleaning sheet 100 in accordance with the present invention may have a layered structure including a polishing layer 101, an elastic layer 102, a synthetic resin film layer 103, an adhesive layer 104, and a releasing paper 105. In the present invention, elastic layer 102 is the PTFE porous body layer. The cleaning sheet may be manufactured to have the above-described layer arrangement and distributed over the market. The user may clean the probe for semiconductor inspection using the cleaning sheet. Typically, the sheet is adhered to some substrate and used for cleaning.

When the cleaning sheet having the layer arrangement shown in FIG. 1 is to be used adhered on a substrate, releasing paper 105 is peeled off, and the sheet is adhered by adhesive layer 104 to the substrate. Specifically, as shown in FIG. 2, a cleaning sheet 200 of the present invention may have a layer arrangement including a polishing layer 201, an elastic layer 202, a synthetic resin film layer 203, an adhesive layer 204, and a substrate 206. In the present invention, elastic layer 202 is the PTFE porous body layer. The adhesive layer may preferably be prepared by applying and half-curing an adhesive, to efficiently perform an operation of adhering to the substrate.

The PTFE porous body used as the elastic layer of the present invention is a PTFE compact made porous, which is generally in a film shape. Generally, synthetic resin porous bodies including the PTFE porous body are formed by various methods, such as pore forming method, phase separation method, solvent extraction method, drawing and laser irradiation. Preferably, the PTFE porous body used in the present invention is a drawn PTFE porous body manufactured by drawing. By drawing, a drawn PTFE porous body having superior heat resistance, cushioning property, processability, mechanical characteristics and dielectric characteristics as well as uniform pore size can readily be obtained.

The drawn PTFE porous body is manufactured in the following manner. First, a mixture of not-yet-sintered polytetra-fluoroethylene powder (fine powder for paste extrusion) and a lubricant (for example, solvent naphtha, petroleum) is compressed in a cylinder and cylindrically preformed. The thus obtained preform is put in an extrusion cylinder, pressed by a ram and extruded from the die, so that an extrusion-molded body in a sheet or rod shape is obtained.

The sheet-shaped or rod-shaped extrusion-molded body resulting from the step of extrusion is rolled by a rolling apparatus such as a roll or a press before the lubricant volatilizes, to form a drawn sheet having a desired thickness. When a thick drawn PTFE porous body is necessary, the sheet-shaped extrusion-molded body may be used in the subsequent step of drawing, without rolling.

The extruded sheet or the rolled sheet is drawn at least in a direction of one axis with the lubricant removed or not removed. If the lubricant is not removed, the lubricant will be removed in a subsequent step such as the drawing step. Generally, drawing is along one-axis or two axes. By the drawing, not-yet sintered PTFE porous body in a sheet shape is obtained. The not-yet sintered drawn PTFE porous film is heated to a temperature not lower than 327° C., which is the melting point of PTFE, while it is fixed to prevent shrinkage, so that the drawn structure is sintered and fixed. Thus, a drawn PTFE porous film with high strength can be obtained.

Alternatively, by putting the above-described preform in an extrusion cylinder and pressing by a ram to be extruded in a form of a tube from the die, and by drawing the tube-shaped extrusion-molded body, a drawn PTFE porous tube can be formed. The drawn PTFE porous tube is sintered in a fixed state, and thereafter cut along the longitudinal direction. Thus, a flat, drawn PTFE porous film can be obtained. The not-yet-sintered drawn PTFE porous tube may be cut to obtain a film, and then the film may be sintered in a fixed state.

The PTFE porous body obtained by drawing has a micro-fibrous texture consisting of very thin fibrils (micro-fibers) and nodes (fine nodes) coupled to each other by the fibrils, both formed of PTFE. In the PTFE porous body, porous structure is formed by the micro-fibrous texture.

By the drawing method, a drawn PTFE porous body having a desired porosity and desired average pore size can be obtained by controlling conditions and the like of drawing. The porosity (ASTM D-792) of the PTFE porous body such as the drawn PTFE porous film used in the present invention is preferably 30 to 90%, more preferably, 40 to 88%, and most preferably, 50 to 85%. The porosity of 30% or higher ensures superior cushioning property (elasticity) of the PTFE porous body layer in various temperature environments. On the other hand, porosity of 90% or lower enhances mechanical strength of the PTFE porous body.

In the cleaning sheet of the present invention, the PTFE porous body having superior cushioning property is arranged under the polishing layer, and therefore, even when the tip ends of probes are brought into press-contact with the polishing layer, soft contact with the polishing layer is possible. The PTFE porous body used in the present invention has superior heat-resistance, and therefore, the PTFE porous body layer has good cushioning property at a room temperature and at a high temperature. In addition, the PTFE porous body layer does not lose its cushioning property at a low temperature of −30° C. or lower, or even at −40° C. or lower.

The PTFE porous body layer used in the present invention has high resin strength, and therefore, even if a tip end of a probe should pierce into the polishing layer, the PTFE porous body layer therebelow would not be torn. Thus, there is no possibility of layer fragments generated as new foreign matter or scattered as dust.

The average pore size of PTFE porous body used in the present invention is preferably 0.01 to 1 μm, more preferably, 0.05 to 0.8 μm and most preferably, 0.1 to 0.5 μm. When the average pore size of PTFE porous body is made 1 μm or smaller, even if the tip end of a probe should pierce into the polishing layer, entrance of the tip end to the pore (into the porous structure) of the PTFE porous body layer therebelow could be prevented. Further, when the average pore size of PTFE porous body is made 1 μm or smaller, it becomes possible to prevent entrance of the tip end to the pore of the PTFE porous body layer, which entrance might result in the tip being caught by the pore and damaged. When the average pore size is made 0.01 μm or larger, cushioning property of the porous body can be improved, and soft contact with the tip end of the probe can be realized.

Thickness of the PTFE porous body layer is typically 10 μm to 1 mm, preferably 30 to 950 μm, and more preferably, 50 to 850 μm. By making the thickness of PTFE porous body layer to be 10 μm or thicker, the cushioning property can be enhanced. When the PTFE porous body is thin, a plurality of not-yet sintered drawn PTFE porous films obtained by the drawing step described above may be stacked, sintered with each layer fixed, with the layers adhered to each other by thermal fusion, whereby a thick and large drawn PTFE porous film with the layers integrated can be obtained. Further, it is preferred that the thickness of the PTFE porous body layer is uniform with as small as possible positional variation, in order to realize uniform contact between each of the probes and the polishing layer and to efficiently perform cleaning. The drawn PTFE porous film obtained by drawing is particularly preferable, as it has excellent film-thickness uniformity with extremely small variation in thickness.

The thickness of the PTFE porous body layer may be rather thick dependent on the manner of use. When the cleaning sheet is used adhered on a substrate, however, it should preferably have the same size and shape as the semiconductor wafer as the object of inspection. Therefore, the sheet should not be excessively thick. The reason is as follows. When the cleaning sheet adhered to the substrate is adapted to have the same size and shape as the semiconductor wafer as the object of measurement, the probes for semiconductor inspection can be cleaned simultaneously in the course of inspecting the electrical characteristics of semiconductor wafers.

As the PTFE porous body has the porous structure, it has superior elasticity (cushioning property) in the thickness direction. Further, as the PTFE porous body has superior heat-resistance, it has superior cushioning property not only at a room temperature but also at a high temperature. Further, the PTFE porous body does not lose its cushioning property at a low temperature of −30° C. or lower, or even at −40° C. or lower. Therefore, the cleaning sheet of the present invention having the PTFE porous body layer as the elastic layer has such cushioning property that allows use in a low temperature environment, for example, of −30° C.

As the polishing layer of the present invention, the polishing layer disclosed in Japanese Utility-Model registration No. 3072423 or Japanese Patent Laying-Open No. 11-238768 described above may be used. Specifically, a thin film for cleaning having fine abrasive powder fixed on the surface, or a metal thin film with its surface made rough may be used. A resin composite layer having fine abrasive powder dispersed in resin is preferable.

The grain size of fine abrasive powder may be appropriately determined dependent on the size and material of the probe for semiconductor inspection. Preferably, it is 0.05 to 5 μm, more preferably, 0.1 to 4 μm, and most preferably, 0.5 to 3 μm. When the grain size of fine abrasive powder is set to be 0.05 μm or larger, efficiency of cleaning foreign matter at the tip end of the probe can be enhanced. On the other hand, when the grain size of fine abrasive powder is set to be 5 μm or smaller, damage and wear of the tip end of the probe can be suppressed.

The material of the fine abrasive powder may be appropriately determined considering the material of the probe for semiconductor inspection. Exemplary material may include aluminum oxide, silicon nitride, boron nitride, silicon carbide, boron carbide and diamond. The fine abrasive powder may be used each by itself or two or more of these may be combined together. The probe for semiconductor inspection is formed by a material having high hardness such as tungsten or palladium alloy. Therefore, the abrasive such as an inorganic fine powder should preferably have the hardness of HV650 or higher in Vickers hardness value. Preferable fine abrasive powder includes, by way of example, silicon carbide #400 (grain size 3 μm), #6000 (grain size 2 μm) and #8000 (grain size 1 μm).

As a binder resin for the fine abrasive powder, one that can firmly bind the fine abrasive powder and is capable of forming a coating film is preferred. Specific examples of the resin may include, by way of example, fluoro-plastic, epoxy resin, urethane resin and enamel. Examples of fluoro-plastic are polytetrafluoro-ethylene (PTFE), tetrafluoro-ethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoro-ethylene-hexafluoro-propylene copolymer (FEP), tetrafluoro-ethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychloro-trifluoroethylene (PCTFE), chloro-trifluoroethylene-ethylene copolymer (ECTFE) and polyvinyl fluoride (PVF).

Epoxy resin may include various types of epoxy resin such as glycidyl ether type, glycidyl ester type, glycidyl amine type and ali-cyclic type. Epoxy resin having small content of hydrolytic chlorine derived from epi-chlorohydrin as the raw material is preferred. As for the urethane resin, any resin having urethane bond in molecular chain may be used, and one having good coating-film-forming capability is preferred.

Enamel refers to a coating of resin capable of forming a coating film used in varnish paint, and examples may include phenolic resin, denatured phenolic resin and terpene resin.

The resin composite layer may be formed by preparing a coating liquid by dispersing or resolving the fine abrasive powder and resin in a solvent, applying the coating liquid on one surface of the PTFE porous body layer, and drying. An additive, for example, a dispersing agent such as a surface-active agent or anti-oxidant may be added to the coating liquid, as needed. The resin composite layer may be formed by preparing a resin composite by melting and blending the fine abrasive powder and resin, and extrusion-molding the resin composite to a sheet. The resulting sheet may be adhered by fusion on one side of the PTFE porous body layer.

The ratio of fine abrasive powder blended with 100 mass parts of resin in the resin composite is, preferably, 10 to 1000 mass parts, more preferably, 30 to 800 mass parts, and most preferably, about 50 to 700 mass parts. When the blending ratio of fine abrasive powder is set to 10 mass parts or higher, cleaning efficiency can be enhanced, and by setting the ratio to 1000 mass parts or lower, adhesiveness of the resin can be made strong.

The thickness of the polishing layer is, preferably, 1 to 100 μm, and more preferably, about 10 to 90 μm. When the thickness of the polishing layer is 100 μm or thinner, cushioning property can be improved by arranging the PTFE porous body layer therebelow, facilitating soft cleaning of the tip end of the probe. When the thickness of the polishing layer is 1 μm or thicker, repetitive cleaning becomes possible.

For the cleaning sheet of the present invention, the adhesive layer may be directly provided below the PTFE porous layer. The adhesive layer is preferably arranged below the PTFE porous body layer with a synthetic resin film interposed, as the adhesive of the adhesive layer does not easily penetrate to the pores of the PTFE porous body layer, and it becomes easier to form the adhesive layer in uniform thickness.

Preferable examples of the synthetic resin include polyimide resin film and thermoplastic polyester resin film. Thermoplastic polyester resin film includes polyethylene terephthalate (PET) film and plybutylene terephethalate (PBT) film. Preferably, such a synthetic resin film is integrated with one surface of the PTFE porous body layer by thermal fusion. The thickness of the synthetic resin film is, typically, about 5 to 30 μm.

By the adhesive layer, the cleaning sheet can be used adhered on a substrate. As the substrate, a hard plate such as a silicon wafer, a ceramic plate or a metal plate is used preferably.

The adhesive of the adhesive layer may be thermosetting resin-based adhesive such as urea resin adhesive, melamine resin adhesive, phenol resin adhesive or epoxy resin adhesive, or thermoplastic resin-based adhesive such as vinyl acetate resin adhesive, ethylene vinyl acetate resin adhesive, acrylic resin adhesive, denatured polyolefin resin adhesive or cyano acrylate adhesive, or rubber-based adhesive such as chloroprene rubber adhesive, nitrile rubber adhesive or styrene butadiene rubber adhesive, or a mixture of these adhesives.

Such an adhesive may be used as a solution type adhesive, emulsion type adhesive, or hot melt type adhesive without solvent. Among these adhesives, one that attains firm adhesion between the synthetic resin film such as the polyimide film or PET film and the substrate described above should preferably be selected. Examples of such adhesive include thermosetting resin-based adhesive such as an epoxy resin adhesive, or thermoplastic resin-based adhesive such as vinyl acetate copolymer emulsion based adhesive, solution type adhesive of synthetic rubber (chloroprene rubber, styrene butadiene rubber, butyl rubber and the like), solution type adhesive of chlorinated polyolefin, and solution type adhesive of denatured polyolefin maleate.

Such an adhesive may be applied to one surface of the synthetic resin film and dried, to form an adhesive layer. A hot melt type adhesive without solvent may be melted and applied to one surface of the synthetic resin film to form an adhesive layer. The adhesive layer may be formed by rubber, acryl or silicone-based glutinous material, though it depends on temperature condition of use of the cleaning sheet and the required adhesiveness.

When an adhesive layer is to be formed using an adhesive and the adhesive is of a thermosetting resin, efficiency of adhering work can be improved by holding the adhesive in not-fully cured but semi-cured state.

The thickness of adhesive layer is, preferably, 5 to 200 μm, more preferably, 10 to 150 μm and most preferably, 25 to 100 μm, though it differs dependent on the type of the adhesive. The thickness of the adhesive layer is set to 5 μm or thicker to enhance adhesive force, and the thickness is set to at most 200 μm to prevent variation in thickness of the cleaning sheet.

The cleaning sheet of the present invention with the adhesive layer provided thereon preferably has the surface of the adhesive layer covered with a releasing paper for protection, as shown in FIG. 1. The releasing paper may be a paper base material such as quality paper, glassine paper or parchment paper with resin anchor-coat, a paper base material coated with a releasing agent such as silicone, quality paper laminated with polyethylene, or a plastic film such as polyethylene or polypropylene film.

As the substrate, a silicon wafer, a ceramic plate, a metal plate or the like as described above may be used. When the cleaning sheet of the present invention has a layered structure including polishing layer 201, elastic layer 202, synthetic resin film layer 203, adhesive layer 204 and substrate 206 as shown in FIG. 2, it is preferred that cleaning sheet 200 has the same size and shape as the semiconductor wafer on which a semiconductor chip is formed. As the sheet is made to have the same size and same shape, a probe tip end can be cleaned simultaneously with the process of semiconductor wafer inspection using the semiconductor inspection probe. The thickness of the entire cleaning sheet having the layered structure shown in FIG. 2 is generally 0.7 to 2.5 mm, and preferably 0.8 to 2.0 mm. The cleaning sheet in accordance with the present invention may have a rectangular or circular shape.

The cleaning sheet of the present invention may be used for removing foreign matter adhered to a tip end of a probe of a probe card used as a wafer prober. The cleaning sheet of the present invention may be used for cleaning probe other than that of the probe card. The cleaning sheet of the present invention has an elastic layer formed of PTFE porous body having superior heat resistance, and therefore, it can be used naturally at a room temperature, and in a high temperature environment of up to 150° C.

Further, the cleaning sheet of the present invention has an elastic layer formed of PTFE porous body of which cushioning property is not lost even at −40° C. Therefore, it may be used for cleaning a probe tip end in a low temperature environment, during inspection of electric characteristics of semiconductor wafers at a low temperature of 0° C. or lower, and even at −30° C. or lower.

In the following, the present invention will be described in grater detail, with reference to an example and a comparative example.

EXAMPLE 1

A coating liquid (solid content concentration: 50 mass %) was prepared by dispersing 40 mass % of silicon carbide (#4000: grain size 3 μm) in aqueous suspension (PFA concentration: 10 mass %) of tetrafluoro-ethylene-perfluoroalkyl vinyl ether copolymer (PFA). On one surface of a drawn PTFE porous body film having porosity of 70%, average pore diameter of 0.3 μm and thickness of 800 μm, a PET film (thickness: 10 μm) was provided by thermal fusion, to form a laminated body. On the surface of drawn PTFE porous film opposite to the PET film, the coating liquid was applied and dried, to form a polishing layer having the thickness of 50 μm. On a surface of the PET film, an epoxy-based adhesive was applied and dried, to form an adhesive layer (thickness: 90 μm). The adhesive layer was semi-cured by heating at 80° C. for 5 minutes. On the adhesive layer, releasing paper (polyethylene-coated quality paper) was placed, and the resulting body was cut to a cleaning sheet A (thickness of entire layers: 1200 μm, width 200 mm×length 200 mm).

The releasing paper was removed from cleaning sheet A, the adhesive layer was put on a silicon wafer (diameter: 300 mm), heated and cured, to form cleaning sheet B having such a layered structure as shown in FIG. 2.

Using cleaning sheet B in a wafer prober, probe tip end was cleaned at a low temperature environment of −30° C. The probe tip end could be softly and efficiently cleaned, and the tip end of the probe was not damaged.

COMPARATIVE EXAMPLE 1

A cleaning sheet having such a layered structure as shown in FIG. 2 was formed using polyurethane in place of drawn PTFE porous body film. The cleaning sheet lost its cushioning property in a low temperature environment of −30° C., and therefore, probe tip end could not be softly cleaned.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims. 

1. A probe cleaning sheet having a layered structure including an elastic layer below a polishing layer, for removing, by contact with the polishing layer, foreign matter adhered on a tip end of a probe for semiconductor inspection, wherein the elastic layer is a polytetrafluoro-ethylene porous body layer.
 2. The probe cleaning sheet according to claim 1, wherein the polytetrafluoro-ethylene porous body layer has porosity of 30 to 90% and average pore diameter of 0.01 to 1 μm.
 3. The probe cleaning sheet according to claim 1, wherein the polishing layer is a resin composition layer containing fine abrasive powder having grain diameter of 0.05 to 5 μm dispersed in resin.
 4. The probe cleaning sheet according to claim 3, wherein the fine abrasive powder is at least one inorganic fine powder selected from the group consisting of aluminum oxide, silicon nitride, boron nitride, silicon carbide, boron carbide and diamond.
 5. The probe cleaning sheet according to claim 3, wherein the resin forming the resin composition layer having fine abrasive powder dispersed is fluoro-plastic, epoxy resin, urethane resin or enamel resin.
 6. The probe cleaning sheet according to claim 1, wherein the layered structure further includes an adhesive layer arranged directly below the polytetrafluoro-ethylene porous body layer or with a synthetic resin film layer interposed therebetween.
 7. The probe cleaning sheet according to claim 6, wherein the adhesive layer is a semi-cured layer of applied adhesive.
 8. The probe cleaning sheet according to claim 6, wherein the layered structure further includes releasing paper arranged below the adhesive layer.
 9. The probe cleaning sheet according to claim 6, wherein the layered structure further includes a substrate adhered to the adhesive layer, below the adhesive layer.
 10. A method of cleaning for removing foreign matter adhered on a tip end of a probe for semiconductor inspection using the probe cleaning sheet according to claim 1 in a low temperature environment of 0° C. or lower. 